An electrochemical cell is a container which has a positive terminal and a negative terminal and is filled with certain chemically active substances. These substances interact with one another to generate a potential difference, i.e., a voltage, between the positive terminal and the negative terminal. The magnitude of this voltage depends principally on the specific chemical interaction which takes place within the cell. For example, a mercury cell generates a voltage of about 1.2 volts due to the interaction of the zinc and mercury oxide contained within the cell.
To obtain a voltage greater than the voltage generated by a single cell, several cells may be assembled in a housing and electrically interconnected so that their voltages add, i.e., connected in series. For example, a 9-volt battery, which is typically used to power a transistor radio, may comprise an assembly of six 1.5-volt cells connected in series. The cells and electrical connectors must be securely maintained in place within the housing in order to avoid short circuits and broken connections and provide a reliable output.
Previous battery assemblies have several undesirable characteristics associated with both the assembly of cells and the cells themselves. For example, many previous battery assemblies consist of as many as 25 or more separate components. Such a large number of components increases the cost and complicates manufacture. In addition, many previous battery assemblies are difficult to assemble not only because they consist of a large number of components but also because the components may fit into the housing in many different ways other than the correct way.
With respect to the cells themselves, the shelf life of many cells utilized in previous battery assemblies is limited. Since there is no way to dissociate the active chemical substances within many cells, chemical interactions within the cell can continue to drain the cells even when the battery assembly is not in use. Further, many cells contain one or more substances which may pose an environmental hazard if it escapes from the cell. For example, the mercury contained in a mercury cell may escape to the environment under extreme operating conditions, such as when the cell is overly discharged.
Metal/air cells have the advantage that the substances utilized within the cell, e.g., zinc and air, are relatively benign to the environment. These cells are also approximately 45 percent lighter than mercury cells. However, previous battery assemblies utilizing metal/air cells frequently include apertures in the housing to provide a source of air for the cells. While these apertures allow air to enter the housing, they may also allow water and objects which may be inserted through the apertures to enter the housing and damage the battery assembly.